Magnetic Suspension Balance Research Articles

Linear Model Predictive Control and Back-Propagation Controller for Single-Point Magnetic Levitation with Different Gap Levitation and Back-Propagation Offline Iteration

Magnetic suspension balance systems (MSBSs) need to allow vehicle models to levitate stably in different attitudes, so it is difficult to ensure the stable performance of the system under different levitation gaps using a controller designed with single balance point linearization. In this paper, a levitation controller based on linear model predictive control and a back-propagation neural network (LMPC-BP) is proposed and simulated for single-point magnetic levitation. The deviation of the BP network is observed and compensated by an expansion state observer (ESO). The iterative BP neural network model is further updated using current data and feedback data from the ESO, and then the performance of the LMPC-BP controller is evaluated before and after the update. The simulation results show that the LMPC-BP controller can achieve stable levitation at different gaps of the single-point magnetic levitation system. With further updating and iteration of the BP network, the controller anti-jamming performance is improved.

Solubility of supercritical CO2 in polystyrene

Expanded polystyrene (ePS) plays an important role in the food packaging industry. However, the foaming process is environmentally unfriendly. A sustainable alternative is dissolving supercritical CO2 (scCO2) in the polystyrene (PS) matrix. Most studies so far were performed at temperatures above the PS glass transition temperature; however, a more general temperature window is desirable. In this work, the solubility of scCO2 in polystyrene was measured at 323 K, 343 K, 363 K and 383 K and pressure up to 130 bar using a magnetic suspension balance (MSB). It was concluded that the solubility of CO2 in PS decreases with temperature and increases with pressure. The Sanchez-Lacombe Equation of State was utilized to estimate the degree of swelling. The model developed was able to derive the experimentally determined solubilities after correction for the swelling. The interaction parameter, k12, turned out to be only a function of temperature. With these results the solubility and swelling of PS in scCO2 can be more accurately assessed for different temperatures and pressures.

CO2 sorption of elastomer poly(ionic liquid)s with imidazolium cations having different alkyl chains: Structure-morphology-property relationships and thermodynamic modelling by the PC-SAFT equation of state

In this work related to Carbon Capture and Storage (CCS), the CO2 sorption capacities of a new family of elastomer poly(ionic liquid)s (PILs) with imidazolium cations having different alkyl chains were studied. These PILs were synthesized by chemical modification of polyepichlorohydrin (polyECH) obtained by living anionic polymerization. PolyECH was quaternized with different 1-alkylimidazoles (alkyl = methyl, n-butyl, and n-hexyl) and followed by anion exchange to obtain three PILs: PIL-Me, PIL-nBu, and PIL-nHex. They were analyzed by NMR (1H, 13C, 2D 1H/13C HSQC, APT 13C) and characterized by SEC, DSC, calorimetry, rheology, and XRD SAXS/WAXS. The influence of the alkyl chain on the PIL CO2 sorption was studied with a magnetic suspension balance (MSB) at 35 °C and CO2 pressures varying from 1 to 10 bar. The best results were obtained with PIL having methyl chains (9.60 mg CO2/g PIL at 1.1 bar and 159.28 mg CO2/g PIL at 10.0 bar at 35 °C). Finally, the CO2 sorption properties of these PILs were modeled with the PC-SAFT equation of state (EoS). The pure-component parameters were obtained from model regression of the PILs densities calculated by the Bondi's and Van Krevelen's methods. The binary interaction parameters of the systems CO2/PIL were optimized with average absolute deviations (AAD) lower than 6.3 % for the three PILs. The PC-SAFT modelling of their sorption properties opens interesting prospects for modelling the CO2 sorption process for CCS facilities.

The Four-Sinker Densimeter: A New Instrument for the Combined Investigation of Accurate Densities and Sorption Phenomena of Pure Gases and Gas Mixtures

An apparatus for high-accuracy gas density and adsorption measurements over the range of temperature from (193 to 423) K and pressure from (0 to 15) MPa is described. This instrument is based on the two-sinker densimetry principle and incorporates a magnetic suspension balance. In addition to the two “density sinkers”, two “sorption sinkers” are weighed to investigate density and adsorption of a gas sample simultaneously. The design of the sinkers increases the resolution of density and adsorption investigations and enables the correction of sorption effects on density measurements. The complete apparatus, including the sinkers, the temperature and pressure measuring systems, and the measurement procedure, is described. For the density range investigated, the uncertainty (k = 2) is between (0.0034 to 0.019) kg·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}m−3, corresponding to (0.060 to 0.011)%. The uncertainty (k = 2) in adsorption load is (0.16 to 0.26) μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}g·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}cm−2. Density measurements at T = (283 and 293) K and pressures up to 10 MPa of high-purity argon and nitrogen validate the instrument for density. Adsorption measurements of high-purity carbon dioxide and propane on a gold surface validate the instrument for adsorption investigation at T = (283 and 293) K and up to the saturation pressure of the investigated gas. The apparatus was used to measure the binary mixture (0.75 CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{CO}_2$$\\end{document} + 0.25 C3H8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{C}_3\ ext{H}_8}$$\\end{document}). In the future, the apparatus will also be used to accurately determine dew-point densities and pressures of pure gases and gas mixtures.

Density, viscosity, and CO2 solubility in ether-functionalized phosphonium-based bis(trifluoromethanesulfonyl)amide ionic liquids

We measured the densities and viscosities of two ionic liquids, triethyl(methoxymethyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P222(1O1)][TFSA]) and triethyl(2-methoxyethyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P222(2O1)][TFSA]), at atmospheric pressure and 273.15–363.15 K. The high-pressure density at the pressures up to 50 MPa was also measured at 298.15–353.15 K. Meanwhile, CO2 solubility in these phosphonium-based ionic liquids was determined using a magnetic suspension balance at 303.15–333.15 K and pressures up to 6 MPa. The experimental density and viscosity at atmospheric pressure were fitted using quadratic and Vogel-Fulcher-Tammann equations, respectively. The high-pressure density was fitted using the Tait equation and Sanchez-Lacombe equation of state. The properties of the two ether-functionalized ionic liquids were compared to those of triethylpentylphosphonium bis(trifluoromethanesulfonyl)amide [P2225][TFSA]. The density at atmospheric pressure increased in the order [P2225][TFSA] < [P222(2O1)][TFSA] < [P222(1O1)][TFSA]. The introduction of the ether group effectively reduced viscosity in the following order: [P222(1O1)][TFSA] < [P222(2O1)][TFSA] < [P2225][TFSA]. The CO2 solubilities in [P222(1O1)][TFSA] and [P222(2O1)][TFSA] were slightly lower than those in [P2225][TFSA]. In contrast, the molality of CO2 (m1) increased in the order [P2225][TFSA] < [P222(2O1)][TFSA] < [P222(1O1)][TFSA]. Ether functionalized phosphonium-based cations are effective in enhancing the physical absorption of CO2, particularly the molality of CO2.

A Novel Triple-actuator Magnetic Suspension Balance System with Enhanced Load and Stability

A Novel Triple-actuator Magnetic Suspension Balance System with Enhanced Load and Stability

Unary Adsorption Equilibria of Hydrogen, Nitrogen, and Carbon Dioxide on Y-Type Zeolites at Temperatures from 298 to 393 K and at Pressures up to 3 MPa.

The equilibrium adsorption of CO2, N2, and H2 on commercially available Zeolite H-Y, Na-Y, and cation-exchanged NaTMA-Y was measured up to 3 MPa at 298.15, 313.15, 333.15, 353.15, and 393.15 K gravimetrically using a magnetic suspension balance. The chemical and textural characterization of the materials was carried out by thermogravimetric analysis, helium gravimetry, and N2 (77 K) physisorption. We report the excess and net isotherms as measured and estimates of the absolute adsorption isotherms. The latter are modeled using the simplified statistical isotherm (SSI) model to evaluate adsorbate-adsorbent interactions and parametrize the data for process modeling. When reported per unit volume of zeolite supercage, the SSI model indicates that the saturation capacity for a given gas takes the same value for the three adsorbents. The Henry's constants predicted by the model show a strong effect of the cation on the affinity of each adsorbate.

Thermal transitions and foaming of a rubbery polymer, poly(ethylene-co-vinyl acetate-co-carbon monoxide), in carbon dioxide: Temperature scaling as a new approach for rational selection of foaming conditions

The foaming of a thermoplastic elastomer, poly(ethylene-co-vinyl acetate-co-carbon monoxide) with varying copolymer compositions was explored using CO2. Copolymers with 0, 10, and 20 wt% vinyl acetate and 10 wt% carbon monoxide, with the remainder being ethylene, designated as EVACO-0010, EVACO-1010, and EVACO-2010 were evaluated. Melting and crystallization temperatures and their depression in CO2 were determined using high-pressure torsional braid analysis. Sorption and swelling assessments were carried out using a modified magnetic suspension balance. Foaming experiments were conducted at 200 bar near the depressed melting and crystallization temperatures. Foams with low (< 0.2 g/cm3) bulk densities of EVACO-1010 and EVACO-2010 were generated near their crystallization temperatures in CO2. A new concept of scaling the foaming temperature with respect to the melting or the crystallization temperature of the polymer in carbon dioxide was developed which provides an insightful new approach for the rational selection of polymer foaming conditions.

Measured CO2 sorption isotherms with 25 Bakken Petroleum System rock samples from the Lower and Upper Shales, Middle Bakken, and Three Forks formations

Isotherms were measured with 25 Bakken Petroleum System (BPS) rock samples using a magnetic suspension balance at reservoir conditions of 110 °C and pressures up to 345 bar. Samples from four wells represented the Middle Bakken (MB) and Three Forks (TF) production zones, and the Upper Bakken Shale (UBS) and Lower Bakken Shale (LBS) source shales. UBS and LBS CO2 sorption capacities at 345 bar averaged 12–14 g/kg rock compared to 1.3 to 2.5 g/kg rock for MB and TF. Increasing pressure from 150 to 345 bar resulted in only small increases in CO2 sorption for all lithofacies. For the UBS and LBS source shales, the higher average total organic carbon (TOC) values (14.7 and 11.4 wt.%) and clay values (25 and 28 wt.%) corresponded to their higher CO2 sorption values while for the MB and TF samples, lower TOCs (0.3 and 0.5 wt.%) and clay values (8.2 and 18.2 wt.%) corresponded to lower CO2 sorption values. When all 25 samples (from all lithofacies) were evaluated as a group, sorption capacities were highly correlated with TOC (Spearman's rho values +0.84 to +0.85), with rock density (rho values -0.75 to -0.76), and clay content (rho values +0.66). However, correlations with porosity and thermal maturity (Tmax) were weak. Measured sorption capacities and rock porosities showed that sorption accounted for about 10-times as much CO2 storage as the available pore space for the UBS and LBS lithofacies. In contrast, the pore space dominated the storage resource of the TF and MB lithofacies.

Investigation On Oxidation Behavior of Nuclear Graphite IG-110 At Elevated Temperature

IG-110 is one of nuclear graphite types for high temperature gas cooled reactor. One of the issues of the graphite in the reactor system is the interaction with air or/and water which can reduce the integrity of the material. In this study, the sample of IG-110 has been tested at high temperature in an air environment. The oxidation test was done using a magnetic suspension balance to analyze the changes in weight with direct monitoring. The test was carried out at a temperature of 630°C. Morphological and microstructural analysis were observed and tested using scanning electron microscope (SEM) and X-ray diffractometer (XRD). The oxidation rate of the sample was relatively low. Rougher sheets shape, larger pores, and slight cracks were observed for the tested sample which indicate the traces of oxidation of the samples with no any critical damage occurred in the sample. Lattice parameters, density, crystal size, and d-space of the sample after oxidation test slightly change, which show the reversible characteristic of the sample from the temperature viewpoint.

Machine Learning-Boosted Design of Ionic Liquids for CO2 Absorption and Experimental Verification.

Efficient CO2 capture is indispensable for achieving a carbon-neutral society while maintaining a high quality of life. Since the discovery that ionic liquids (ILs; room-temperature molten salts) can absorb CO2, various solvents composed of molecular ions have been studied. However, it is challenging to observe the properties of each isolated ion component to control the function of ILs as they are mixtures of ions. Finding the optimal cation-anion combination for the CO2 absorbent from their enormous chemical space had been impossible in a practical sense. This study applied electronic structure informatics to explore ILs with high CO2 solubility from 402,114 IL candidates. The feature variables were determined by a set of cheap quantum chemistry calculations for isolated small-ion fragments, and the importance of molecular geometries and electronic states governing molecular interactions was identified via the wrapper method. As a result, it was clearly shown that the electronic states of ionic species must have essential roles in the CO2 physisorption capacity of ILs. Considering synthetic easiness for the candidates narrowed by the machine learning model, trihexyl(tetradecyl)phosphonium perfluorooctanesulfonate was synthesized. Using a magnetic suspension balance, it was experimentally confirmed that this IL has higher CO2 solubility than trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide, which is the previous best IL for CO2 absorption.

A Disturbance Force Compensation Framework for a Magnetic Suspension Balance System

The research on the dynamic characteristics of vehicles requires wind tunnel tests. The natural mass frequency of the support mechanism and the interference of the support mechanism on the flow field will greatly reduce the repeatability and accuracy of the experimental results. The magnetic suspension and balance system (MSBS) uses non-contact electromagnetic force instead of mechanical support to eliminate the support mechanism’s interference with the test results. The MSBS needs to actively adjust the electromagnetic force to control the position of the tested model. At present, its control strategy is PID control. However, when the wind tunnel is opened, there will be large aerodynamic loads, leading to large changes in displacement. We propose a disturbance compensation control algorithm framework that can quickly estimate the external force disturbance and quickly compensate it to the control loop, reduce the influence of the disturbance on the control system, and provide stability and accuracy of displacement control.

Mass Transport in the Stefan-Knudsen Transition Region during Vacuum Drying at Different Pressures in a Porous Structure Resembling Battery Electrodes.

A precise understanding of the mass transport kinetics of water inside the porous structure of battery electrodes is crucial to understanding and optimizing their post-drying process. This process and the moisture management during the production of Li-ion battery electrodes adjust and remove residual water from electrodes and are cost intensive. Furthermore, the amount of residual moisture in the electrode affects device performance. Mass transport phenomena in the Stefan and Knudsen transition affect these processes. In this manuscript, we investigate the mass transport in the interparticle gas phase of a porous structure gravimetrically by a magnetic suspension balance with a conditioned (humidity, temperature, and pressure) measurement cell. Emphasis lies on the pressure, porosity, and mass transport distance dependency of the desorption process. Comparing experimental data with a simulation of the interparticle gas phase shows that the mass transport close to ambient pressure can be described by Stefan diffusion through the porous structure. The experiments show the significance of Knudsen diffusion during the mass transport toward lower pressure. A proposed diffusion-coefficient model describes the Stefan and Knudsen region with a transition function, taking the mass transport phenomena overlap into account by lower and upper limits as transition values.

Numerical study of bubble nucleation and growth of N2 in low density polyethylene

Bubble nucleation and growth were investigated in low density polyethylene (LDPE) using nitrogen (N2). The solubility and diffusivity of N2 in low density polyethylene were determined by a magnetic suspension balance (MSB) system. The bubble nucleation and growth during foaming was assessed using a visualization batch foaming system. It was observed that the increase in temperature and pressure decrement, decreased the bubble density, respectively. The bubble size during the foaming was also studied through numerical model and the effect of various simulation variables on the bubble growth was investigated. It was concluded that the numerical model could predict the foaming process. Moreover, according to the bubble pressure profile, the N2diffusion are formative factors in controlling the bubble growth.

Development of a Compact Magnetic Suspension Balance

This article develops a prototype of magnetic suspension balance (MSB) for mass measurement, in which the mass of the sealed sample is transferred to the measuring unit via the magnetically suspended method. Considering that the excitation current decides the magnetic force while the magnetic force balances the gravity of the detected object, a type of compact MSB can be obtained by combining the force sensor unit and the magnetic suspension coupling unit (MSCU). Many efforts are undertaken to improve the performance of the compact MSB. The design parameters of the MSCU are optimized to decrease the sensitivity of the magnetic force to the variation in the suspension height; the magnetic suspension system is regulated by an active disturbance rejection control method to decrease the current fluctuation in the stator coil; the calibration method founded on the least-squares method is used to suppress the data drifts existed in the measuring process. The testing results show that both the resolution and repeatability of the MSB reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$500~\mu \mathrm {g}$ </tex-math></inline-formula> , and the measuring uncertainty is less than 1 mg for the weights up to 1 g.

Thermodynamic property measurements and modelling of CO2 + difluoromethane (R32): Density, heat capacity, and vapour-liquid equilibrium

Accurate thermodynamic property data and models are demanded to reduce the design margins of industrial processes based on these fluids. In this work, measurements of density (ρ), heat capacity (cp), and vapour-liquid equilibrium (VLE) for CO2 + difluoromethane (R32) have been performed by the vibrating tube densimeter and the magnetic suspension balance densimeter, the visual cell and gas chromatograph, and the differential scanning calorimeter, respectively. Experiments were conducted over the temperatures ranging from (208.3 to 334.3) K and pressures reaching 10.04 MPa at CO2 concentrations of 0.7, 0.8 and 0.9. The measured data, together with the results reported in literature where applicable, were subsequently applied to regress the binary interaction parameters utilised in the mixture functions of Helmholtz energy model from REFPROP 10 software package. Noticeable improvements have been achieved for the model's ability to represent thermodynamic property data. The most significant achievement exists in density description: compared with the default parameters, the root-mean-square (RMS) deviation has been decreased by half.

Diffusivities and solubilities of carbon dioxide in deep eutectic solvents

Deep eutectic solvents (DESs) have been identified as promising solvents for CO2 capture because of their low volatility and tunable properties. Detailed information on solute solubility and diffusivity is crucial for the design and operation of processes involving mixtures composed of DESs and dissolved gases. The infinite-dilution diffusion coefficients of CO2 in 33 DESs (both hydrophilic and hydrophobic) were gravimetrically determined with a magnetic suspension balance at 298.15 and 313.15 K along with the Henry’s constants of CO2 in these DESs. Interestingly, the diffusion coefficients of CO2 at infinite dilution in hydrophobic DESs were found to be much higher than those in hydrophilic DESs. In order to better understand this phenomenon, CO2 diffusion coefficients under infinite dilution conditions in traditional solvents and ionic liquids (ILs) were summarized from literature, which revealed that the CO2 diffusivity is often approximately inversely proportional to the square root of the viscosity. However, the hydrophilic DESs and some ILs/hydrophobic DESs with large molar volumes displayed a significantly different behavior. The OH group seems to hinder CO2 diffusion, while the presence of multiple long flexible alkyl chains in the DES constituents can facilitate the diffusion. Modified Wilke–Chang correlations were successfully developed to describe the infinite-dilution diffusion coefficients in the measured DESs. Tetraoctylammonium bromide - decanoic acid (1:2) was found promising for further investigation for application in CO2 capture processes with supported liquid membranes or physical absorption.

Evidence of iso-volume deformation during convective drying of yacón: An extended van Meel model adapted to large volume reduction

This work investigates the drying of yacón (Smallanthus sonchifolius), a source of fructooligosaccharides and inulin, two prebiotic compounds. Experiments were performed using an in-house device consisting of a magnetic suspension balance coupled to a drying chamber and an in-situ shadowgraphy system. This allowed the continuous acquisition of mass, sample volume and exchange surface area to be register versus time at different temperatures (50–70 °C) and relative humidities (10%–30%), which was never done with yacón. Once corrected by the actual area of the exchange surface, the drying kinetics (kg.s−1.m−2) depicts two phases, a very long constant drying rate flux and a falling drying rate flux. Even though yacón samples lost up to 91% of their initial volume, an iso-volume deformation was observed: the reduction of sample volume equals the volume of removed water. Thanks to these two experimental facts, an extended, original, van Meel model is proposed to account for this huge change of sample shape in a predictive way.

Effect of gelatin on the solubility and diffusivity of normal pentane in the poly (vinyl alcohol)/Gelatin blends

In this work, we investigated the effect of Gelatin on the solubility and diffusivity of normal pentane in poly (vinyl alcohol) (PVA)/Gelatin (Gel) blends. The processibility of PVA was enhanced after adding the gelatin as plasticizer to PVA which gelatin could extend the process widow of PVA with destroying the hydrogen bonding of the polymer matrix. Therefore, the PVA/Gel blends with different concentrations were prepared by simple solution-casting method. The intermolecular suitable interactions in PVA/Gel blends were confirmed using the FTIR, XRD and SEM/EDX analyzes. In the following, the effect of various factors like temperature, pressure and gelatin content on the thermodynamic parameters like specific free volume, solubility and diffusivity was investigated. It was shown that there was a relationship between the specific free volume of the blends with the solubility and diffusivity of normal pentane in blends. The specific free volume of blends was determined by applying the PVT data and the Sanchez-Lacombe (SL) equation of state, in which it was enhanced with increasing of the temperature and gelatin in blends, respectively. Also, the solubility and diffusivity of normal pentane in samples were determined by the magnetic suspension balance (MSB) system. The results presented that the solubility and diffusivity of n-pentane improved with increasing of gelatin content in blend, pressure and temperature decrement, respectively.

Water effect on adsorption carbon capture in metal-organic framework: A molecular simulation

Considering water vapor is a component in almost all CO2-rich industrial gas streams, it is of critical importance to understand interaction mechanisms between adsorbent and adsorbate. This paper aims to comprehensively analyze water effect on CO2 adsorption for metal-organic framework (MOF) in a broad working pressure range which may bring some new insights based on a molecular simulation. First, Mg-MOF-74 is selected and synthesized according to previous literature. Equilibrium adsorption capacity and enthalpy are obtained by grand canonical Monte Carlo simulation, and the results for high-pressure CO2 adsorption are validated through magnetic suspension balance experiment. It is indicated that there are three adsorption stages for pure CO2 and four adsorption stages for pure H2O under different pressure. Adsorption enthalpy also varies with adsorption capacity, which is fully explained from the angle of adsorption stages and energies. Further simulation of flue gas (CO2/H2O/N2) adsorption at different humidity are carried out, and selectivity between CO2 and H2O is analyzed. At 298 K, 100 kPa, with 3% water content, CO2/H2O selectivity is 5.6 × 10−5. When temperature rises to 388 K, CO2/H2O selectivity rises to 6.2 × 10−3. Adsorption density distributions, simulation snapshots, and radial distribution functions are used in analysis processes, which could provide a general perspective for analyzing CO2 adsorbents in the presence of H2O.